This invention relates to an improvement in commonly owned previous U.S. Pat. No. 5,211,869 issued May 18, 1993. This issued patent describes a mixture of calcium halide salts, ground to a fine powder, then combined into a pellet form on a pan agglomerater using as the preferred agglomerating solution, a magnesium chloride solution. The finished product was then dried. The drying process itself was difficult and expensive, making that pan agglomerated product difficult to competitively price with other competing products.
While pan agglomeration achieves significant advantages in terms of product performance of those agglomerates, those advantages are insufficient to justify the large price differential caused by the expensive drying process. It can therefore be seen that it would be desirable to have a pan agglomeration process achieving the advantages of the agglomerates resulting from pan agglomeration, i.e., substantially spherical, highly porous, low bulk density fast ice melters, but doing so without the added economics of a separate and distinct heating step. Achieving such is a primary objective of this invention.
Much effort has gone towards achieving the above primary objective of the present invention, and it involved many trial and error steps. Those steps involved exploring changes in concentrations and content of the agglomerating solution, changes in ground fine powder content from which the agglomerates are made, changes in a source of the material used, and finally, experimentation with fully hydrated, partially hydrated, dehydrated or anhydrous salts. Anhydrous salts refer to those in which the water of hydration is completely driven off. Partially hydrated salts refer to those in which only a portion of the water of hydration is driven off. Fully hydrated refers to the salts having maximum number of water of hydration molecules associated with the salt. For example calcium chloride may exist in an anhydrous form, a monohydrate, a dihydrate or a hexahydrate. Anhydrous form refers to no molecules of water of hydration and the hexahydrate refers to a fully hydrated calcium chloride.
After exploring all of the above possible alternatives it has been discovered that the key to preparing a successful pan agglomerated product achieving all the normal objectives and advantages of pan agglomeration without having an expensive drying process is to use as the source material for the fine dry powder anhydrous or partially anhydrous halide salts of metals selected from the group consisting of alkali metals and alkaline earth metals. In so doing, the water used in the pan agglomerating fluid hydrates the fine ground powder as agglomeration is occurring making the agglomerates appear physically dry thus avoiding the necessity for a separate heating and drying step.